It is always amusing (especially with Game of Thrones) when book purists get in a tissy over a supposed change from the books when that "change" wasn't actually a change at all, but instead just something that wasn't specified in the books.
Speaking of book purists reading into things, on
www.winteriscoming.com, book purists are in a tissy because Catelyn apparently expresses regret about being mean to Jon and saying that a lot of the bad things that happened to her family are her fault (a review called it bordering on character assassination and these people agree). In their mind Catelyn is a hero that treated Jon like any other person would have and if Robb had only listened to her then everything would have been great. I really don't know what book people are reading to get that impression of Catelyn. The list of Catelyn follies is a mile long heh.
If anything, showing her onscreen with some regret will have us mourning her loss at the RW instead of wondering how she managed to live that long already.